Maize grain yields were significantly higher following one to three years of Stylosanthes than after natural fallow or repeated cropping. This demonstrates an important benefit of the forage legume in addition to its value as a ruminant feed supplement. The implications for the development of traditional agro-pastoral production systems are discussed.

A computer technique for predicting the yields of the component crops in intercropping systems is described. Predictions using this procedure showed reasonable agreement with results obtained in an experiment using tomatoes and dry beans. Reasons for the discrepancies observed and limitations to the applications of the technique are discussed.

Differences in the growth and development of five genotypes of chickpea (Cicer arietinum) were studied until the three branch stage (18 or 21 days after sowing). Seedlings were grown in nutrient solution in clear Perspex cells immersed in temperature controlled water baths. Daily removal and photographing allowed serial measurements of the rate of root extension to be made. An accurate, detailed description of the rooting pattern was obtained by sectioning along the primary axis after harvest. Significant differences between the genotypes in root and shoot growth were recorded. The Syrian local landrace, ILC 1929, and the Ascochyta blight resistant genotype, ILC 428, had faster rates of extentions of the primary root axis and of lateral root development than the other genotypes. The possible significance of these results to subsequent growth and yield in Mediterranean environments is discussed.

Field trials are described in which the seed yield response of row-sown sesame to increasing plant population was examined, and in which row-sowing was compared with broadcasting at different seed rates. Maximum yields were obtained at an intended 200 to 250 × 103 plants ha−1 but yields were not greatly affected by a wider range of populations. Broadcasting, the normal local practice, gave yields slightly higher than those from rows 50 cm apart, the un-thinned rate of 800 × 103 viable seeds sown ha−1 yielded as well as treatments thinned to the optimum population, and double this seed rate, unthinned, gave the lowest yields, especially in rows.

Field trials are described in which sesame varieties maturing in 125 days at 2 m high, were grown in alternate rows with sorghum maturing in 175 days at 4 m. Compared to sowing both crops together, the yield of sesame sown 10, 14 and 28 days after sorghum fell by 53, 68 and 100%, respectively, but sorghum yield was not consistently affected. Improved sesame varieties, despite being shorter and less branched, performed better than the local variety, and nitrogen fertilizer applied to one or both components of the mixture did not appear to favour one crop at the expense of the other.

The response of sesame to fertilizer was studied in 11 trials at four different sites, in which phosphorus was applied at rates from 0 to 26 kg ha−1 to the seed bed and nitrogen at rates from 0 to 60 kg ha−1 after thinning. Yield responses, found only to the main effects of nitrogen and phosphorus, are discussed in relation to soil type and previous cropping history of the sites and used to calculate gross cash returns from fertilizer use. Seed oil content was affected by environment, but responses to nitrogen and phosphorus were inconsistent.

Smallholders in south-east Tanzania grow the groundnut Red Mwitunde (Arachis hypogaea ssp. hypogaea), a long-season variety with seed dormancy, although earlier maturing varieties with no seed dormancy (ssp. hypogaea and fastigiata) usually yielded better in trials, particularly when late sown. Small-seeded, short-season varieties established better in the field than Red Mwitunde and other large-seeded varieties, especially under moisture stress. Trials with selective fungicides to estimate yield losses from leafspots (mainly Cercosporidium personatum) and rust (Puccinia arachidis), jointly and separately, showed no consistent varietal differences.

Variety × spacing and variety × sowing date trials in south-east Tanzania showed that the long-season spreading bunch groundnut variety Red Mwitunde (A. hypogaea ssp. hypogaea var. hypogaea) was less tolerant of delayed sowing and more tolerant of wide spacing than Natal Common, a short-season upright bunch variety (ssp. fastigiata var. vulgaris). The same variety × spacing and variety × sowing date interactions were detected in groundnuts intercropped with cassava (Manihot esculenta). These observations help to explain the farmers' preference for Red Mwitunde despite the higher trial yields of Natal Common.

Stands of pearl millet were grown in three controlled environment glasshouses in which were imposed different combinations of atmospheric saturation deficit (1.5 to 2.3 kPa) and soil water content (fully irrigated and not irrigated). Consistent differences in saturation deficit (SD) were maintained throughout the experiment (100 days) but a high water table restricted differences in water supply to the first 40 days. Responses to SD and soil water were observed in some variables but not in others. Developmental processes such as the rate of leaf appearance were unaffected, whereas the efficiency for conversion of intercepted solar energy decreased by 24% and the rate at which the canopy expanded by 50%, in the driest compared to the wettest conditions.

The effects of sowing pattern and seed rate on the green-chop yield of forage sorghum-sudangrass hybrid (cv. Pioneer 988) and forage sorghum (cv. Abu Sabeen) were investigated. In general, more green-chop yield was obtained from seed of both cultivars drilled in regular rows, double rows and triple rows than when traditionally sown as broadcast seed. Yields were greater when plants were sown at 70 kg seed ha−1 than when traditionally sown at 35 kg seed ha−1. These yield advantages were sustained through three successional harvests. Pioneer 988 generally yielded more than Abu Sabeen, especially when sown in January. Both cultivars gave minimum yield when sown in April, July or October.

Field trials on okra over three seasons showed that the removal of the apical bud on the main stem at 3 or 4 weeks did not affect marketable fruit yield but that yield was reduced by about 39% when debudding was done at 5, 6 or 7 weeks. Apical debudding led to increased vegetative development, enhanced dry matter accumulation and reduced plant height. Removing the apical bud at weeks 3, 4 or 5 delayed the first harvest by 8, 15 or 18 days, respectively, compared to the undebudded control plants. It appears that okra can tolerate considerable apical damage during the vegetative stage, as can happen with insect attack, without serious loss of yield.